-LRB- CNN -RRB- -- Since March 11 , the six reactors at the Fukushima Daiichi nuclear power plant have been in various states of disrepair after being battered by a 9.0-magnitude earthquake and subsequent tsunami .

Here is the latest on the status of each reactor and what was being done to prevent further emissions of radioactive material .

Reactor No. 1

Pressure and temperature levels at the No. 1 reactor continue to fluctuate , though Hidehiko Nishiyama of Japan 's nuclear and industrial safety agency told reporters Friday that the situation then appeared `` rather stable . ''

While conceding that `` controlling the temperature and pressure has been difficult , '' Nishiyama said there were indications that the pressure and temperature were both decreasing .

Authorities hope to begin injecting fresh water , rather than seawater as has been done , into the reactor 's spent nuclear fuel pool .

According to the Japan Atomic Industrial Forum , a nuclear industry group basing its data on official government and utility information , the No. 1 unit 's reactor core has been damaged , but its containment vessel was not . As of Friday , the reactor 's cooling systems were still not operational .

Still , the building was `` severely damaged '' by an earlier hydrogen explosion .

While electricity issues remain , lighting has been restored for this and the No. 2 reactors .

Reactor No. 2

Like with No. 1 , there has been evidence of high radiation levels in spots in and around the No. 2 reactor -- though not as high as that of the No. 3 unit .

Nishiyama said Friday that authorities hope to start injecting fresh water -LRB- rather than the current seawater -RRB- into the reactor 's core and spent nuclear fuel pool . The water is being pumped in to help cool down nuclear fuel rods and prevent the further emission of radioactive material .

Damage is `` suspected '' in this unit 's containment vessel -- the only such vessel so compromised , according to the Japan Atomic Industrial Forum . The reactor 's core is also thought to be damaged . But the building itself has only been `` slightly damaged , '' the same group reports .

That said , the containment vessel pressure is considered `` stable , '' the nuclear industry trade group reports .

Reactor No. 3

The water that three men stepped in while laying cable in the basement of the No. 3 unit 's turbine building had 10,000 times the amount of radiation typical for that locale , Nishiyama said . The workers -- each of whom tested 170 or more millisieverts of radiation , including two with direct exposure on the skin -- were admitted Friday for four days of observation at Japan 's National Institute for Radiological Sciences , a research hospital in Chiba .

He noted that the contamination likely came from the reactor 's core , adding there 's a possibility of `` some sort of leakage . '' That potentially could come from a crack in the reactor core , though Nishiyama cautioned that there is no definitive answer yet on how the radioactivity got into the basement .

Despite the suspected damage to the reactor core -- something that is n't presumed at any of the other five reactors -- the nuclear safety official said there is evidence that pressure is somehow being maintained in the vessel , making it less likely there is a big gash .

`` Radiation levels are high '' in some locations in and around the reactor , Nishiyama said .

These issues , including the radiation in the water , are prompting authorities to consider `` other routes '' to address issues at the reactor without exposing workers to excess radiation . Nishiyama said that , as of Friday afternoon , there was no firm plan on workarounds .

Firefighters from Kawasaki , with assistance from the Tokyo fire department , sprayed water Friday on the No. 3 reactor and its spent nuclear fuel pool .

The building of the No. 3 reactor was `` severely damaged '' after an explosion caused by the buildup of hydrogen gas , reports the Japan Atomic Industrial Forum . Its core reactor is also damaged , its fuel rods are either partly or fully exposed . As to its nuclear spent fuel pool , reports are that the pool was `` possibly damaged '' and the water level has been low -- a reason for the repeated spraying .

Reactor No. 4

A concrete pump truck was used once again Friday to inject seawater into the unit 's fuel pool .

Along with the Nos. 5 and 6 units , the No. 4 was offline on a scheduled outage when the earthquake hit , and as a result the reactor 's water level and pressure are continued safe .

But its nuclear spent fuel pool was `` possibly damaged , '' which is why authorities have said its water levels are low and why they 've made repeated efforts to fill it up with seawater .

Reactor No. 5

The No. 5 unit appears safe , for now , Nishiyama said . Its capability to cool the fuel rods in the spent fuel pool is working again , according to the Japan Atomic Industrial Forum .

As with units Nos. 4 and 6 , this reactor was off on a scheduled outage when the quake hit and there are no major issues with the reactor and core itself . The nuclear spent fuel pool is thought to be functioning , aside from continued concerns about powering its cooling system to ensure that the fuel rods contained within remain cool .

As with unit No. 6 , three holes were punched in the building earlier in order to relieve pressure and prevent a hydrogen explosion .

Reactor No. 6

The No. 6 unit appears safe , for now , Nishiyama said . Its capability to cool the fuel rods in the spent fuel pool is working again , according to the Japan Atomic Industrial Forum .

The No. 6 reactor was offline when the tsunami struck , and there are no major concerns about the structure or safety of its core or containment vessel . The nuclear spent fuel pool is thought to be functioning , aside from continued concerns about powering its cooling system to ensure that the fuel rods contained within remain cool .

As with unit No. 5 , three holes were punched in the building earlier in order to relieve pressure and prevent a hydrogen explosion .

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The Nos. 1 and 3 reactors are prime concerns at the northeastern Japan plant

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Authorities are trying to determine the source of an apparent leak in reactor No. 3

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An official says No. 1 seems `` rather stable '' after challenges with heat and pressure